Gas streams rich in hydrogen sulfide are needed for many industrial processes such as hydrometallurgical processes and in the conversion of sulfur dioxide contained in flue gases to sulfur.
Two processes are known to have been used industrially for production of H.sub.2 S.
In one, elemental sulfur is reacted with high-purity hydrogen at temperatures from 800.degree. F. to 1000.degree. F. A deficiency of the process is that the required high-purity hydrogen is costly, being made by steam reforming of expensive fuels such as methane or selected light napthas. An even greater deficiency is that neither of these may be available at a location where the H.sub.2 S is needed. Severe corrosion of metal alloy equipment has been experienced.
Another involves mixing sulfur vapor with methane and heating the mixture to a temperature about 1250.degree. F. to 1350.degree. F. in fired tubes. Corrosion of the tube walls is a serious problem, since the tube walls are necessarily at a higher temperature to enable heat transfer through the tube walls.
The above processes entail that excess sulfur exists in the gas mixture after reaction. When the reaction products are cooled, sulfur condenses out above the melting point of sulfur. It is, however, usually necessary to cool the gas to about ambient temperature before use, and in cooling from the sulfur melting point to ambient temperature solid sulfur deposits on heat transfer surfaces and blocks the transfer of heat, thereby presenting serious practical problems.
A need exists, therefore, for a process to produce hydrogen sulfide from a low cost fuel, which avoids problems of fouling by excess sulfur and high-temperature corrosion of metals by sulfur and sulfur compounds.